KR101084520B1 - Fast Frequency Hopping Using Code Division Multiplexing Pilot in an OPDMA System - Google Patents

Abstract

Techniques are provided to support fast frequency hopping with code division multiplexed (CDM) pilot in a multi-carrier communication system (eg, OFDMA system). Each transmitter (eg, each terminal) in the system transmits a wideband pilot on all subbands, allowing the receiver (eg, base station) to estimate the overall channel response simultaneously. A wideband pilot for each transmitter may be generated using direct sequence spread spectrum processing and based on a pseudo random number (PN) code assigned to that transmitter. This allows the receiver to individually identify and recover multiple broadband pilots transmitted simultaneously by multiple transmitters. In a time division multiplexing (TDM) / CDM pilot transmission scheme, each transmitter transmits a wideband pilot in bursts. In a continuous CDM pilot transmission scheme, each transmitter transmits a wideband pilot continuously despite a low transmit power level. Any frequency hopping rate may be supported without affecting pilot overhead.

Frequency hopping, OFDMA

Description

FAST FREQUENCY HOPPING WITH A CODE DIVISION MULTIPLEXED PILOT IN AN OFDMA SYSTEM}

Cross Reference of Related Application

This application is filed in pending US Provisional Patent Application No. 60 / 470,107, filed May 12, 2003, entitled "Fast Frequency Hopping with a Code Division Multiplexed Pilot in an OFDMA System", incorporated herein by reference. Insist on priority.

background

Technical Field

TECHNICAL FIELD The present invention relates generally to communications and, more particularly, to techniques for supporting fast frequency hopping using code division multiplexed (CDM) pilots in orthogonal frequency division multiple access (OFDMA) communication systems.

Background

In a frequency hopping spread spectrum (FHSS) communication system, data is transmitted on different frequency subbands or on sub-carriers of different time intervals called a "hop period". Such frequency subbands may be provided by orthogonal frequency division multiplexing (OFDM), other multi-carrier modulation techniques, or some other configurations. In FHSS, data transmission hops from subband to subband in a pseudo-random manner. This jump provides frequency diversity and allows the data transmission to better tolerate harmful path effects such as narrowband interference, jamming, fading, and the like.

An OFDMA system uses OFDM and can support multiple users simultaneously. In a frequency hopping OFDMA system, data for each user is transmitted using a particular frequency hopping (FH) sequence assigned to the user. The FH sequence indicates the specific subband to use for data transmission in each hop period. Multiple data transmissions for multiple users may be sent simultaneously using different FH sequences. These FH sequences are defined to be orthogonal to each other so that only one data transmission uses each subband in each hopping period. By using orthogonal FH sequences, interference inside the cell is avoided, and multiple data transmissions do not interfere with each other while enjoying the benefits of frequency diversity.

An OFDMA system may be deployed in multiple cells, where the cells typically represent a base station and / or its coverage area. Data transmission on a given subband in one cell acts as interference to another data transmission on the same subband of an adjacent cell. In order to randomize inter-cell interference, the FH sequences for each cell are typically defined to be pseudo random with respect to the FH sequences for neighboring cells. By using pseudo random FH sequences, interference diversity is achieved and data transmission for a user in a given cell will maintain average interference from data transmissions for other users in other cells for a sufficiently long period of time. .

Intercell interference can vary significantly from subband to subband at any given moment. To account for variation in interference across subbands, a margin is typically used to select a data rate for data transmission. In the case of large variability in interference, a large margin is generally required to achieve a low packet error rate (PER) for data transmission. Large margins result in greater reductions in data rate for data transmission, which limits system capacity.

Frequency hopping can average the intercell interference and reduce the required margin. Increasing the frequency hopping rate results in a better interference average and reduces the required margin. The fast frequency hopping rate is particularly advantageous for certain types of transmissions where other techniques such as automatic retransmission request (ARQ) cannot be used to encode data over multiple frequency hops and mitigate the deleterious effects of interference. .

Frequency hopping rate is typically limited by channel estimation requirements. In an OFDMA system, the channel response for each subband used for data transmission is typically estimated by the receiver, and the channel response estimate for the subband is used to coherently demodulate the data symbols received on that subband. do. Channel estimation for each subband is generally accomplished based on pilot symbols received on the subband. In a fast fading communication channel, the fading rate generally prevents the receiver from combining pilot symbols received on the same subband from previous hops. Thus, to independently estimate the channel response for each hop period, a sufficient number of pilot symbols are required to be transmitted in the hopping period so that the receiver can obtain a sufficiently accurate channel response estimate. These pilot symbols represent a fixed overhead for each hop period. In this case, increasing the frequency hopping rate also increases pilot overhead.

Accordingly, there is a need in the art for techniques that support fast frequency hopping without increasing pilot overhead in OFDMA systems.

summary

Provided herein is a technique for supporting fast frequency hopping using a CDM pilot in a multi-carrier communication system (eg, an OFDMA system). Each transmitter (eg, each terminal) in the system transmits a wideband pilot on all subbands, allowing the receiver (eg, base station) to estimate the overall channel response simultaneously. A wideband pilot for each transmitter may be generated using direct sequence spread spectrum processing and based on a pseudo random number (PN) code assigned to that transmitter. This allows the receiver to individually identify and recover multiple broadband pilots transmitted simultaneously by multiple transmitters. In a time division multiplexed (TDM) / CDM pilot transmission scheme, each transmitter transmits a wideband pilot in bursts. In a continuous CDM pilot transmission scheme, each transmitter transmits a wideband pilot continuously but at a low transmit power level.

At the transmitter, one or more symbols are processed with the PN code assigned to the transmitter to obtain a sequence of pilot chips for the wideband pilot. The data symbols are processed according to a multi-carrier modulation scheme (eg OFDM) to obtain a sequence of data chips. When data symbols are transmitted with frequency hopping, the specific subband to use for the data symbols in each hopping period is determined by the FH sequence assigned to the transmitter. In the TDM / CDM pilot transmission scheme, the sequence of pilot chips is time division multiplexed with the sequence of data chips to obtain a TDM sequence of pilot and data chips, which are further processed and transmitted. In a continuous CDM pilot transmission scheme, the sequence of pilot chips is summed with the sequence of data chips to obtain a sequence of combined pilot and data chips, which sequence is further processed and transmitted.

At the receiver, a sequence of initially received chips is obtained. In the TDM / CDM pilot transmission scheme, the sequence of received chips is demultiplexed to obtain a sequence of received pilot chips and a sequence of received data chips. A sequence of received pilot chips (for a TDM / CDM pilot transmission scheme) or a sequence of received chips (for a continuous CDM pilot transmission scheme) is processed with a PN code assigned to the transmitter to multiplex from the transmitter to the receiver. Obtain a time domain channel gain estimate for the propagation paths. The rake receiver may be used for pilot processing at the receiver. The channel gain estimate is further processed (eg, interpolated) and transformed to obtain a frequency domain channel response estimate for the multiple subbands.

In a continuous CDM pilot transmission scheme, pilot interference cancellation may be performed (based on channel gain estimates) on a sequence of received chips to obtain a sequence of received data chips. In both pilot transmission schemes, the sequence of received data chips or the sequence of received chips (if available) is processed according to the multi-carrier demodulation scheme (eg, scheme for OFDM) and the channel response estimate. To obtain recovered data symbols, which is an estimate of the data symbols transmitted by the transmitter. In the case where data symbols were transmitted with frequency hopping, the specific subband for obtaining the recovered data symbols in each hopping period is determined by the same FH sequence used at the transmitter.

The techniques described herein can provide various advantages including the ability to support any frequency hopping rate without affecting pilot overhead. In practice, the frequency hopping rate may be as fast as one OFDM symbol per hopping period. The fast frequency hopping rate may improve the interference average and reduce the required margin, which may improve the system's usable capacity.

Hereinafter, various aspects and embodiments of the present invention will be described in more detail.

Brief description of the drawings

The features, properties and advantages of the present invention will become apparent from the following detailed description with reference to the drawings in which like reference numerals generally identify correspondingly.

1 illustrates a conventional pilot transmission scheme for a frequency hopping OFDMA system.

2 shows a TDM / CDM pilot transmission scheme.

3 shows a continuous CDM pilot transmission scheme.

4 illustrates an example OFDMA system.

5A and 5B show block diagrams of a terminal and a base station, respectively.

6A and 6B show a block diagram of a transmit (TX) pilot processor and a timing diagram for a TDM / CDM pilot transmission scheme, respectively.

6C and 6D show a block diagram of a TX pilot processor and a timing diagram for a continuous CDM pilot transmission scheme, respectively.

7A shows a block diagram of a receive (RX) pilot processor for a TDM / CDM pilot transmission scheme.

7B and 7C show a block diagram of an RX pilot processor and a block diagram of a pilot interference canceller, respectively, for a continuous CDM pilot transmission scheme.

8A shows a process for transmitting a wideband pilot in the TDM / CDM pilot transmission scheme.

8B shows a process for transmitting a wideband pilot in a continuous CDM pilot transmission scheme.

8C shows a process for receiving a wideband pilot in a TDM / CDM pilot transmission scheme.

8D shows a process for receiving a wideband pilot in a continuous CDM pilot transmission scheme.

details

The term "example" is used herein to mean "an example, provided by way of example, illustration." Embodiments or designs described herein as "examples" need not be construed as preferred or advantageous over other embodiments or designs.

In the following description, the "channel gain estimate" is a time-domain estimate of the complex channel gain for the propagation path from the transmitter to the receiver. A "channel frequency response estimate" (or simply, "channel response estimate") is a frequency-domain estimate of the channel response for a particular subband of a communication channel between a transmitter and a receiver. (The communication channel may include multiple propagation paths.) As mentioned above, the channel gain estimate may be processed and transformed to obtain a channel response estimate. A "channel estimate" can collectively represent a channel gain estimate, a channel response estimate, or some other type of estimate for a communication channel.

The OFDMA system uses OFDM, a multi-carrier modulation technique that effectively partitions the overall system bandwidth into multiple (N) orthogonal subbands. These subbands are also commonly referred to as tone, sub-carrier, bin and frequency subchannels. Using OFDM, each subband is associated with each sub-carrier, which may be modulated with data. In some OFDM systems, only N _data subbands are used for data transmission, N _pilot subbands are used for pilot transmission, N _guard subbands are not used, and the guard sub is allowed to allow the system to meet spectral mask requirements. It functions as bands, where N = N _data + N _pilot + N _guard . For simplicity, the following description assumes that all N subbands can be used for data transmission.

1 shows a conventional pilot transmission scheme 100 for a frequency hopping OFDMA system. 1 shows pilot and data transmission in the frequency-time plane, with the vertical axis representing frequency and the horizontal axis representing time. In this example, N = 8 and eight subbands are allocated with indices of 1-8. Up to eight traffic channels may be defined, with each traffic channel using one of eight subbands in each hopping period. The hopping period is a duration consumed in a given subband and may be defined to be equal to one or multiple OFDM symbols.

Each traffic channel is associated with a different FH sequence. FH sequences for all traffic channels may be generated with the FH function f (k, T), where k represents the number of traffic channels and T represents the system time given in units of hopping periods. N different FH sequences may be generated with N different k values of the FH function f (k, T). The FH sequence for each traffic channel indicates the specific subband to use for the traffic channel in each hop period. For clarity, FIG. 1 shows the subbands used for one traffic channel. In Figure 1, it can be seen that this traffic channel hops from subband to subband in a pseudo-random manner determined by the FH sequence.

In the conventional pilot transmission scheme 100, a group of P pilot symbols (indicated by a dark box) is transmitted in a TDM scheme with a group of data symbols (indicated by a diagonal box) in each hopping period, where P≥1. Typically, P is the number of pilot symbols required to allow the receiver to estimate the channel response independently in each hop period. P pilot symbols represent the fixed overhead required for each hop period. This fixed overhead becomes a greater percentage of the transmission as the hop period decreases. Thus, the frequency hopping rate is limited by pilot overhead.

In this specification, pilot transmission schemes suitable for use in fast frequency hopping in a multi-carrier transmission system are provided. Such pilot transmission schemes are suitable for use on the reverse link, but may also be used for the forward link. For clarity, the pilot transmission schemes are described in detail below for the reverse link of an OFDMA system.

2 shows a TDM / CDM pilot transmission scheme 200 for a frequency hopping OFDMA system. In this pilot transmission scheme, each user transmits a wideband pilot that is time division multiplexed with the user's data transmission. The wideband pilot is transmitted on all N subbands and allows the receiver (eg, base station) to estimate the total channel response at the same time. The wideband pilot may be generated in the time domain using direct sequence spread spectrum processing, as described above.

The wideband pilot has a duration of T _p seconds, or T _p = N _p · T _s , where N _p is the number of OFDM symbol periods in which the wide band pilot is transmitted and T _s is the duration of one OFDM symbol. In the example shown in FIG. 2, T _p = 2 · T _s , where one hop period corresponds to one OFDM symbol period. In general, the pilot duration T _p is chosen long enough to allow the receiver to obtain a sufficiently accurate channel response estimate for each of the users. The pilot duration T _p may depend on various factors such as the amount of transmit power available to each user, the worst case channel conditions expected for all users, and the like.

The wideband pilot is transmitted every T _w seconds and has a periodicity of T _w seconds. For the example shown in FIG. 2, T _w = 14 · T _s . In general, the pilot period T _w may be selected to be shorter than the coherence time τ of the communication channel, ie, T _w <τ. Coherence time is a time interval at which the communication channel is essentially constant. By selecting T _w <τ, the channel response estimate can be guaranteed to be valid for the entire T _w seconds between wideband pilot bursts.

In the TDM / CDM pilot transmission scheme, the pilot overhead is determined by the pilot duration T _p and the pilot periodicity T _w that depend on the particular characteristics of the communication channel (eg, coherence time). This pilot transmission scheme can support any frequency hopping rate without affecting pilot overhead. In practice, the frequency hopping rate may be as fast as one OFDM symbol (ie, symbol-rate hopping) per hopping period, which is highly desirable for the reasons described above.

As shown in FIG. 2, the wideband pilot for each user is transmitted in bursts and does not interfere with data transmission for that user. To avoid pilot to data interference for all users in the cell, users can transmit their wideband pilots at the same time interval. In this case, wideband pilots for all users of each cell will not interfere with their data transmissions. Also, because users use orthogonal FH sequences, the data transmissions of all users in each cell will not interfere with each other.

Transmission of broadband pilots by all users at the same time means that these broadband pilots will interfere with each other. To mitigate pilot to pilot interference, wideband pilots for all users may be "orthogonalized". Orthogonalization of broadband pilots may be accomplished in various ways, some of which are described below.

In one embodiment, the pilot symbol for each user is "covered" with an orthogonal code unique to that user. Covering is the process by which the pilot symbol to be transmitted is multiplied by all W chips of the W-chip orthogonal code to obtain W covered chips, the W covered chips being further processed and transmitted. The orthogonal code may be a Walsh code, an orthogonal variable spreading factor (OVSF) code, a quasi-orthogonal function (QOF), or the like. The covered pilot for each user is then spread out over all N subbands with a PN code common to all users. In general, any PN code with features typically associated with a good PN code (eg, flat spectral response, low or zero cross correlation at different time offsets, etc.) may be used for spectral spreading. The PN code may also be called a scrambling code or some other terminology.

In yet another embodiment, the pilot symbol for each user is spread out over all N subbands with a PN code unique to that user. In this embodiment, the PN code is used for both orthogonalization and spectral spreading. User specific PN codes may be defined with different time shifts of a common PN code, similar to the use of different time shifts of short PN codes for different base stations in IS-95 and IS-2000 systems. In this case, a unique time shift is assigned to each user, and the PN code for that user can be identified by the assigned time shift. The common PN code may be represented as PN (n), the time shift assigned to user x may be represented as ΔT _x , and the PN code for user x may be represented as PN (n + ΔT _x ).

In both embodiments, the wideband pilot for each user is code division multiplexed and time division multiplexed. For clarity, an embodiment is described in which a wideband pilot for each user is spread out with a user specific PN code to suppress pilot interference from other users.

Referring to FIG. 2, a wideband pilot is transmitted using CDM, and data transmission is transmitted using OFDM. Hereinafter, processing at the transmitter and the receiver for the CDM / TDM pilot transmission scheme will be described.

3 shows a continuous CDM pilot transmission scheme 300 for a frequency hopping OFDMA system. In this pilot transmission scheme, each user continuously transmits a broadband pilot that is overlaid (ie added) on the data transmission. In addition, a wideband pilot is transmitted on all N subbands, allowing the receiver (eg, base station) to estimate the overall channel response.

Consecutive wideband pilots may be transmitted at low power levels while allowing the receiver to obtain high quality channel response estimates. This is because, similar to the gain achieved in a CDMA system, the receiver can integrate / accumulate many received pilot chips to realize significant signal processing gain from CDM integration. Since the communication channel is coherent over multiple OFDM symbol periods, integration across many received pilot chips is possible.

Successive broadband pilots for each user interfere with each other. Similar to the TDM / CDM pilot transmission scheme, wideband pilots for all users may be orthogonalized to mitigate pilot to pilot interference. The orthogonalization and spectral spreading of the broadband pilot for all users may be accomplished with (1) different orthogonal codes and common PN codes, or (2) different user specific PN codes, as described above. For clarity, the following description assumes that the wideband pilot for each user is orthogonalized and spread to the user specific PN code to suppress pilot interference from other users.

In addition, successive wideband pilots for each user interfere with data transmissions for other users as well as data transmissions for that user. This pilot-to-data interference is shown in FIG. 3 and the boxes for the data symbols are shaded to indicate that the broadband pilot overlaps on these data symbols. However, as mentioned above, only a small amount of transmit power is required for successive broadband pilots for each user. Thus, due to broadband pilots for all users, the total pilot interference observed by the data transmission for each user is small. In addition, as described above, the receiver may estimate and cancel interference due to wideband pilots.

In the continuous CDM pilot transmission scheme (and TDM / CDM pilot transmission scheme), the pilot overhead is determined by the amount of transmission power used for wideband pilot versus the amount of transmission power used for data transmission. Thus, the pilot overhead is fixed and does not depend on the frequency hopping rate. The continuous CDM pilot transmission scheme can support any frequency hopping rate (including symbol-rate hopping) without affecting pilot overhead.

In both the TDM / CDM pilot transmission scheme and the continuous CDM pilot transmission scheme, wideband pilots from each user are typically transmitted at a predetermined power level. However, the wideband pilot may also be transmitted at a power level that may be controlled by a closed power control loop.

4 illustrates an example OFDMA system 400 that supports multiple users. System 400 includes a number of base stations 410 that provide communication to a number of terminals 420. A base station is a fixed station used to communicate with terminals and may be referred to as a base station transceiver subsystem (BTS), access point, Node B, or some other terminology. Typically, terminals 420 are dispersed throughout the system, and each terminal may be stationary or mobile. A terminal may also be called a mobile station, user equipment (UE), wireless communication device, or some other terminology. Each terminal may communicate with one or more base stations on the forward link and / or may communicate with one or more base stations on the reverse link at any given moment. This depends on whether the terminal is active, whether soft handoff is supported and whether the terminal is in soft handoff. The forward link (ie downlink) refers to the communication link from the base station to the terminal, and the reverse link (ie uplink) refers to the communication link from the terminal to the base station. For simplicity, only transmissions on the reverse link are shown in FIG. 4.

The system controller 430 couples to the base stations 410, where (1) coordination and control for these base stations, (2) routing of data between these base stations, and (3) are served by the base stations It may also perform a number of functions such as access and control of terminals.

5A shows a block diagram of an embodiment of a terminal 420x that is one of the terminals in the OFDMA system 400. For simplicity, only the transmitter portion of terminal 420x is shown in FIG. 5A.

Within terminal 420x, encoder / interleaver 512 can receive traffic data from data source 510 and control that data and other data from controller 540. Encoder / interleaver 512 formats, encodes, and interleaves the received data to provide coded data. Modulator 514 then modulates the coded data according to one or more modulation schemes (eg, QPSK, M-PSK, M-QAM, etc.) to provide modulation symbols (or simply “data symbols”). do. Each modulation symbol is a complex value for a particular point in the signal constellation for the modulation scheme used for that modulation symbol.

OFDM modulator 520 performs frequency hopping and OFDM processing on data symbols. Within OFDM modulator 520, TX FH processor 522 receives the data symbols and provides these data symbols on the appropriate subbands determined by the FH sequence for the traffic channel assigned to terminal 420x. . This FH sequence indicates the specific subband to use in each hop period and is provided by the controller 540. In the TDM / CDM pilot transmission scheme, the TX FH processor 522 provides data symbols only during data transmission periods as shown in FIG. In a continuous CDM pilot transmission scheme, the TX FH processor 522 provides data symbols continuously for each hop period, as shown in FIG. In this case, data symbols dynamically jump from subband to subband in a pseudo-random manner determined by the FH sequence. For each OFDM symbol period, TX FH processor 522 provides N "transmit" symbols for the N subbands. These N transmit symbols consist of one data symbol for the subband used for data transmission (when data is transmitted) and a zero signal value for each subband not used for data transmission.

A Fast Fourier Inverse Transform (IFFT) unit 524 receives N transmit symbols during each OFDM symbol period. The IFFT unit 524 then transforms the N transmit symbols into the time domain using an N-point IFFT to obtain a "converted" symbol that includes the N time domain "data" chips. Each data chip is a complex value that is transformed in one chip period. (The chip rate is related to the overall bandwidth of the system.) The cyclic prefix generator 526 receives N data chips for each transformed symbol and repeats a portion of the transformed symbols to repeat N + C _p data chips. To form an OFDM symbol, where C _p is the number of data chips to be repeated. The repeated portion is often called a cyclic prefix and is used to suppress intersymbol interference (ISI) caused by frequency selective fading. The OFDM symbol period corresponds to the duration of one OFDM symbol, which is N + C _p chip periods. Cyclic prefix generator 526 provides a stream of data chips for the stream of OFDM symbols.

A transmit (TX) pilot processor 530 receives a stream of data chips and one or more pilot symbols. TX pilot processor 530 generates a wideband pilot that is time division multiplexed with the data chips (for the TDM / CDM pilot transmission scheme) or superimposed on the data chips (for the continuous CDM pilot transmission scheme). TX pilot processor 530 provides a stream of "sending" chips. In the TDM / CDM pilot transmission scheme, each transmit chip is a data chip or a pilot chip. In the continuous CDM pilot transmission scheme, each transmit chip is a sum of a data chip and a pilot chip. Transmitter unit 532 (TMTR) processes the stream of transmit chips to obtain a modulated signal that is transmitted from antenna 534 to the base station.

5B is a block diagram of an embodiment of base station 410x, which is one of the base stations in OFDMA system 400. For simplicity, only the receiver portion of base station 410x is shown in FIG. 5B.

The modulated signal transmitted by terminal 420x is received by antenna 552. The signal received from the antenna 552 is provided to a receiver unit 554 (RCVR) and processed to provide samples. Receiver unit 554 may further perform sample rate conversion (from receiver sampling rate to chip rate), frequency / phase correction, and other preprocessing for the samples. Receiver unit 554 provides a stream of "received" chips.

A receive (RX) pilot processor 560 receives and processes the stream of received chips to recover the wideband pilot and data chips transmitted by terminal 420x. Some designs for the RX pilot processor 560 are described below. RX pilot processor 560 provides the stream of received data chips to OFDM demodulator 570 and provides a channel gain estimate to digital signal processor 562 (DSP). DSP 562 processes the channel gain estimates to obtain channel response estimates used for data demodulation as described above.

Within OFDM demodulator 570, cyclic prefix removal unit 572 receives the stream of received data chips and removes the cyclic prefix appended to each received OFDM symbol to obtain the received transformed symbol. FFT unit 574 then transforms each received transformed symbol into the frequency domain using an N-point FFT to obtain N received symbols for the N subbands. RX FH processor 576 obtains N received symbols for each OFDM symbol period and provides the received symbols from the appropriate subbands as received data symbols for that OFDM symbol period. The specific subband for obtaining the received data symbol in each OFDM symbol period is determined by the FH sequence for the traffic channel assigned to terminal 420x. This FH sequence is provided by the controller 590. Since data transmission by terminal 420x dynamically jumps from subband to subband, RX FH processor 576 operates in conjunction with TX FH processor 522 in terminal 420x and from appropriate subbands Provides received data symbols of. The FH sequence used by RX FH processor 576 in base station 410x is the same as the FH sequence used by TX FH processor 522 in terminal 420x. Also, the FH sequences at base station 410x and terminal 420x are synchronized. RX FH processor 576 provides a demodulator 580 with a stream of received data symbols.

Demodulator 580 receives the received data symbols and coherently demodulates them with a channel response estimate from DSP 562 to obtain reconstructed data symbols. The channel response estimate relates to the subbands used for data transmission. Demodulator 580 further demaps the recovered data symbols to obtain demodulated data. Deinterleaver / decoder 582 then deinterleaves and decodes the demodulated data to provide decoded data that may be provided to data sink 584 for storage. In general, processing by units at base station 410x is complementary to processing performed by corresponding units at terminal 420x.

Controllers 540 and 590 direct operation at terminal 420x and base station 410x, respectively. Memory units 542 and 592 provide storage for data and program codes used by controllers 540 and 590, respectively. Also, the controllers 540 and 590 may perform pilot related processing. For example, the controllers 540 and 590 may determine the time intervals at which the wideband pilot for terminal 420x should be transmitted and received, respectively.

5A and 5B illustrate the transmission and reception of pilot and data on the reverse link, respectively. Similar or different processing may be performed for pilot and data transmissions on the forward link.

6A is a block diagram of a TX processor 530a that may be used for the TDM / CDM pilot transmission scheme. TX pilot processor 530a is an embodiment of TX pilot processor 530 in FIG. 5A and includes pilot generator 610, multiplier 616, and multiplexer 618 (MUX).

Within pilot generator 610, multiplier 612 receives pilot symbols and multiplies with PN code PN _x (n) to provide a stream of pilot chips. The pilot symbol may be any real or complex value known a priori by both terminal 420x and base station 410x. PN code PN _x (n) is a code assigned to terminal 420x, where “n” is the chip index. The PN code may be represented as PN _x (n) = PN (n + ΔT _x ) in embodiments in which each user is assigned a different time shift ΔT _x of the common PN code PN (n). Multiplier 614 receives the stream of pilot chips and scales it to scaling factor K _p and provides a stream of scaled pilot chips. Multiplier 616 receives the stream of data chips and scales with scaling factor K _d and provides a stream of scaled data chips. Scaling factors K _p and K _d determine the transmit powers used for wideband pilot and data symbols, respectively. Multiplexer 618 receives the stream of scaled data chips, multiplexes with the stream of scaled pilot chips and provides a stream of transmit chips. Multiplexing is performed in accordance with the TDM control provided by controller 540.

6B shows a timing diagram for a TDM / CDM pilot transmission scheme. The transmit chips from TX pilot processor 530a are composed of pilot chips and time division multiplexed data chips. TDM control determines when data chips and pilot chips are provided as transmit chips. The length of PN code PN _x (n) may be chosen to be equal to the duration of one wideband pilot burst, which is N _p · (N + C _p ) chips. In addition, the PN code length may be selected to be equal to the duration of the multiple OFDM symbols, the duration of the multiple broadband pilot bursts, or some other duration.

6C shows a block diagram of a TX pilot processor 530b that may be used for the continuous CDM pilot transmission scheme. TX pilot processor 530b is another embodiment of TX pilot processor 530 in FIG. 5A and includes pilot generator 620, multiplier 626, and summer 628.

Within pilot generator 620, multiplier 622 receives the pilot symbol and multiplies the PN code PN _x (n) assigned to terminal 420x and provides a stream of pilot chips. Multiplier 624 receives the stream of pilot chips and scales it to scaling factor K _p and provides a stream of scaled pilot chips. Multiplier 626 receives the stream of data chips and scales with scaling factor K _d and provides a stream of scaled data chips. Summer 628 receives the stream of scaled data chips, sums it with the stream of scaled pilot chips, and provides a stream of transmit chips.

6D shows a timing diagram for the continuous CDM pilot transmission scheme. The transmit chips from TX pilot processor 530b are composed of data chips superimposed (ie, added) on the pilot chips. The length of the PN code PN _x (n) may be chosen to be equal to the duration of one OFDM symbol, which is N + C _p chips. In addition, the PN code length may be chosen to be equal to the duration of some OFDM symbols or some other duration.

6A and 6C illustrate the generation of a wideband pilot in the time domain using direct sequence spread spectrum processing. In addition, a wideband pilot may be generated in other ways, which is within the scope of the present invention. For example, a wideband pilot may be generated in the frequency domain. In this embodiment, the pilot symbol may be transmitted on each of the N subbands during the pilot burst for the TDM pilot transmission scheme or continuously for the continuous pilot transmission scheme. The N pilot symbols on the N subbands are orthogonalized with an orthogonal code or a PN code, allowing the base station to individually identify and recover multiple frequency domain broadband pilots transmitted simultaneously by multiple terminals.

7A shows a block diagram of an RX pilot processor 560a that may be used for the TDM / CDM pilot transmission scheme. RX pilot processor 560a is one embodiment of RX pilot processor 560 in FIG. 5B and includes a demultiplexer 712 and a rake receiver 720.

Demultiplexer 712 receives a stream of chips received from receiver unit 554 and demultiplexes these chips in a manner complementary to the multiplexing performed by terminal 420x. Demultiplexing is performed with TDM control provided by controller 590 as shown in FIG. 6B. Demultiplexer 712 provides the received data chips to OFDM demodulator 570 and provides the received pilot chips to rake receiver 720.

The received signal at base station 410x may include multiple instances (or multipath components) of a modulated signal transmitted by terminal 420x. Each multipath component is associated with a specific complex channel gain and time of arrival to a particular base station 410x. The channel gain and arrival time for each multipath component is determined by the propagation path for that multipath component. A searcher (not shown in FIG. 7A) searches for strong multipath components in the received signal and provides the timing of each found multipath component with sufficient strength. The searcher correlates the received chips with PN code PN _x (n) at various time offsets to search for strong multipath components, similar to search processing performed in a CDMA system. Search techniques for discontinuous (ie gated) pilots are described in US Patent Application No. 09 / 846,963, filed May 1, 2001 and entitled “Method and Apparatus for Searching a Gated Pilot” .

Rake receiver 720 includes M finger processors 722a through 722m, where M> 1. Each finger processor 722 may be assigned to process different multipath components found by the searcher. Within each assigned finger processor 722, multiplier 724 multiplies the received pilot chips with the delayed PN code PN _x (n + τ _i ) and provides the despread chips. PN code PN _x (n + τ _i ) is a delayed version of PN code PN _x (n) assigned to terminal 420x, where τ _i corresponds to the arrival time of the i-th multipath component processed by the finger processor Is a time offset. Accumulator 726 (ACC) then accumulates despread chips for N _acc chip periods and provides a channel gain estimate G _i for the assigned multipath component. The accumulation interval N _acc is determined by ACC control and may be selected to be equal to the pilot burst duration, PN code length, or some other time interval. (The pilot burst duration may or may not be the same as the PN code length.) The M finger processors 722a through 722m estimate M channel gains for up to M different multipath components with different time offsets. Can provide up to. Multiplexer 728 multiplexes channel gain estimates from assigned finger processors 722. The channel gain estimate from rake receiver 720 represents a non-uniformly spaced time domain channel impulse response for the communication channel for terminal 420x, where the spacing is determined by the time offset τ _i associated with this channel gain estimate. .

FIG. 7A also shows DSP 562a, which is an embodiment of DSP 562 in FIG. 5B. Within DSP 562a, interpolator 752 receives the channel gain estimate from rake receiver 720, performs interpolation on the non-uniformly spaced channel gain estimate, and estimates the channel for terminal 420x. N chip spaced gain values representing the impulse response are provided. Interpolation of the channel gain estimate is performed based on the associated time offset tau _i . Interpolation may also be performed using linear interpolation or some other known interpolation technique. FFT unit 754 receives N chip-spaced gain values from interpolator 752, performs an N-point FFT on these N gain values, and provides N frequency domain values. These N frequency domain values are estimates of the channel response for the N subbands of the communication channel for terminal 420x.

For the TDM / CDM pilot transmission scheme, wideband pilots are transmitted in bursts and data symbols are transmitted between these pilot bursts, as shown in FIG. FFT 754 provides a channel response estimate for each wideband pilot burst. Interpolator 756 receives and interpolates channel response estimates from FFT 754 and provides interpolated channel response estimates for each subband used for data transmission. Interpolator 756 may perform linear interpolation or some other type of interpolation. Demodulator 580 coherently demodulates the received data symbols using the interpolated channel response estimate. In addition, interpolator 756 may simply provide a channel response estimate derived from the nearest pilot burst for each subband used for data transmission.

7B shows a block diagram of an RX pilot processor 560b that may be used for the continuous CDM pilot transmission scheme. RX pilot processor 560b is another embodiment of RX pilot processor 560 in FIG. 5B and includes a rake receiver 720 and an optional pilot interference canceller 730.

Pilot interference canceller 730 receives a stream of chips received from receiver unit 554 and processes the chips in a manner to be described below to provide the received data chips. In the absence of a pilot interference canceller 730, the received chips may be provided directly as received data chips. Rake receiver 720 receives and processes the received chips in the manner described above with respect to FIG. 7A. The accumulating interval N _acc for each accumulator 726 may be selected for one OFDM symbol period, multiple OFDM symbol periods, PN code length, or some other time interval. M finger processors 722a through 722m in rake receiver 720 may provide up to M channel gain estimates for the estimated channel impulse response for terminal 420x.

DSP 562b receives and processes the channel gain estimate from rake receiver 720 to provide a channel response estimate for terminal 420x. DSP 562b includes interpolator 762, FFT unit 764, and filter 766. Interpolator 762 and FFT unit 764 operate in the manner described above for interpolator 752 and FFT unit 754 in FIG. 7A, respectively. Filter 766 filters the channel response estimate and provides a filtered channel response estimate for each subband used for data transmission. Demodulator 580 coherently demodulates the received data symbols using the filtered channel response estimate.

7C is a block diagram of an embodiment of a pilot interference canceller 730 in an RX processor 560b. Pilot interference canceller 730 includes K pilot interference estimators 760a through 760k, where K ≧ 1. Each pilot interference estimator 760 may be used to estimate pilot interference due to one terminal. For clarity, one pilot interference estimator 760x is used to estimate the pilot interference from terminal 420x.

Pilot interference estimator 760x includes M pilot generators 762a-762m and summer 768. Each pilot generator 762 may be assigned to a different multipath component processed by the rake receiver 720, that is, one pilot generator 762 is associated with each assigned finger processor 722. The multipath component assigned to each pilot generator 762 is associated with the channel gain estimate G _i and the delayed PN code PN _x (n + τ _i ) provided by the associated finger processor 722. Within each pilot generator 762, the pilot symbol is multiplied by the PN code PN _x (n + τ _i ) delayed by multiplier 764, and also multiplied by the channel gain estimate G _i by multiplier 766 to assign it. The pilot chip estimates for the multipath components. Summer 768 then adds the pilot chip estimates from all assigned pilot processors 762 and provides pilot interference due to terminal 420x.

Summer 770 receives and sums pilot interference for all terminals being processed and provides total pilot interference. Summer 772 subtracts the total pilot interference from the received chips to provide the received data chips.

8A shows a flowchart of a process 810 for transmitting a wideband pilot in a TDM / CDM pilot transmission scheme in a wireless multi-carrier communication system (eg, an OFDMA system). One or more pilot symbols are processed with the PN code (eg, in the time domain using direct sequence spread spectrum processing) to obtain a sequence of pilot chips for the wideband pilot (step 812). The PN code is used to spread the pilot symbol and uniquely identify the transmitting entity of the wideband pilot. The data symbols are processed according to a multi-carrier modulation scheme (eg, OFDM) to obtain a sequence of data chips (step 814). In the case where data symbols will be transmitted with frequency hopping, the specific subband to use for the data symbols in each hopping period is determined by the FH sequence. The sequence of pilot chips and the sequence of data chips may be scaled into two scaling factors to control the transmit powers for wideband pilot and data symbols. The sequence of pilot chips is time division multiplexed with the sequence of data chips to obtain a TDM sequence of pilot and data chips (step 816). The TDM sequence of pilot and data chips is further processed and transmitted (step 818).

8B is a flowchart of a process 830 for transmitting a wideband pilot in a continuous CDM pilot transmission scheme in a wireless multi-carrier communication system. One or more pilot symbols are processed into a PN code to obtain a sequence of pilot chips (step 832). Data symbols are processed to obtain a sequence of data chips (step 834). Steps 832 and 834 correspond to steps 812 and 814 in FIG. 8A, respectively. The sequence of pilot chips is summed with the sequence of data chips to obtain a combined sequence of pilot and data chips (step 836). The sequence of combined pilot and data chips is further processed and transmitted (step 838).

8C is a flow diagram of a process 850 for receiving a wideband pilot transmitted in a TDM / CDM pilot transmission scheme in a wireless multi-carrier communication system. A sequence of received chips is obtained (step 852) and demultiplexed to obtain a sequence of received pilot chips and a sequence of received data chips (step 854). The received sequence of pilot chips is processed with a PN code (eg, using a rake receiver) to obtain channel gain estimates for multiple propagation paths (step 856). This PN code is a code assigned to the transmitting entity with which the wideband pilot is processed. The channel gain estimate is further processed (eg, interpolated) to obtain a sequence of chip-spaced gain values, after which the chip-spaced gain values are transformed to obtain channel response estimates for multiple subbands. (Step 858).

The received sequence of data chips is processed according to a multi-carrier demodulation scheme (e.g., OFDM) and channel response estimate to obtain recovered data symbols that are estimates of data symbols transmitted by the transmitting entity (step 860). If the data symbols were transmitted in frequency hopping, the specific subband for obtaining the recovered data symbols in each hopping period is determined by the same FH sequence used at the transmitting entity.

8D shows a flowchart of a process 870 for receiving a wideband pilot transmitted in a continuous CDM pilot transmission scheme in a wireless multi-carrier communication system. A sequence of received chips is obtained that includes a sequence of combined pilot and data chips transmitted by a transmitting entity (step 872). The received sequence of chips is processed with a PN code for the transmitting entity to obtain a channel gain estimate (step 874). The channel gain estimate is further processed to obtain a channel response estimate for the plurality of subbands (step 876).

Pilot interference cancellation may be performed on the sequence of received chips to obtain a sequence of received data chips (step 878). Step 878 is optional and indicated by dashed boxes. Pilot interference cancellation is performed by (1) estimating interference due to the wideband pilot and (2) canceling the estimated interference from the sequence of received chips to obtain a sequence of received data chips. Pilot interference due to multiple transmitting entities may be estimated and canceled in a similar manner. A sequence of received data chips (if pilot interference cancellation has been performed) or a sequence of received chips (if pilot interference cancellation has not been performed) is processed according to the multi-carrier demodulation scheme and the channel response estimate to recover the recovered data symbols. (Step 880).

The CDM pilot transmission scheme described herein can provide various advantages over an OFDMA system. For the TDM / CDM pilot transmission scheme, the receiver can derive an estimate of the entire wideband channel in one pilot transmission. For a continuous CDM pilot transmission scheme, even if a user is transmitting data and frequency hopping, the receiver can derive an estimate of the entire wideband channel. For both pilot transmission schemes, the frequency hopping rate no longer affects pilot overhead. In addition, data transmission may hop at any frequency hopping rate, including one hop per OFDM symbol period.

 Since wideband pilots are CDM pilots, OFDMA systems also benefit from the various advantages of CDMA systems. These advantages are:

Faster power control;

Soft handoff (performance is better if the base station is synchronized); And

Better time resolution, and thus better time tracking.

Modulated signals from multiple terminals may be received simultaneously by the base station. The CDM pilot for each terminal may be processed to obtain various measurements for the terminal, such as receive pilot strength, timing and frequency recovery. These measurements may be used to support power control, soft handoff, and other functions. Typically, the transmit power of each terminal is controlled such that the modulated signal received at the base station does not occupy the full dynamic range of a particular component (eg, ADC) in the receiving unit of the base station. Since pilot processing is performed on a chip instead of an OFDM symbol, faster power control may be achieved with a CDM pilot. Faster power control may provide improved performance for all terminals. In addition, improved time resolution may be obtained from performing pilot processing at the chip level instead of the OFDM symbol level. Soft handoff may also be facilitated more easily using improved pilot signal strength measurements from the CDM pilot.

The techniques described herein may be used in frequency hopping OFDMA systems and other wireless multi-carrier communication systems. For example, such techniques may be used in a system using other multi-carrier modulation techniques such as discrete multi-tone (DMT). The CDM pilot may be used with or without frequency hopping.

The techniques described herein may be implemented by various means in the transmitter and the receiver. Pilot and data processed at the transmitter and receiver may be performed in hardware, software, or a combination thereof. For hardware implementations, processing units (e.g., TX pilot processor 530, RX pilot processor 560, DSP 562, etc.) may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital devices. In a signal processing device (DSPD), programmable logic device (PLD), field programmable gate array (FPGA), processor, controller, micro-controller, microprocessor, other electronic unit designed to perform the functions described herein. May be implemented in or a combination thereof.

For software implementations, pilot and data processing at the transmitter and receiver may be implemented as modules (eg, processes, functions, etc.) that perform the functions described herein. The software code may be stored in a memory unit (eg, memory units 542 and 592 in FIGS. 5A and 5B) and executed by a processor (eg, controllers 540 and 590). The memory unit may be implemented within the processor or external to the processor, in which case the memory unit can be communicatively coupled with the processor via various known means.

The foregoing embodiments are provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the generic principles defined in the specification can be applied to other embodiments without departing from the scope of the present invention. Thus, the present invention is not limited to the above-described embodiments, but rather provides the broadest scope consistent with the principles and novel features disclosed herein.

Claims (35)

A method of transmitting a wideband pilot in a wireless multi-carrier communication system, the method comprising: Processing one or more pilot symbols with a pseudo random number (PN) code to obtain a sequence of pilot chips for the wideband pilot; Processing the data symbols according to a multi-carrier modulation scheme to obtain a sequence of data chips; Time division multiplexing the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips; And Transmitting a TDM sequence of the pilot and data chips, The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Wide band pilot transmission method. The method of claim 1, And wherein said wireless multi-carrier communication system is an orthogonal frequency division multiple access (OFDMA) communication system and said multi-carrier modulation scheme is orthogonal frequency division multiplexing (OFDM). The method of claim 1, Wherein the one or more pilot symbols are spread spectrum into the PN code in the time domain using direct sequence spread spectrum processing to obtain the sequence of pilot chips. The method of claim 1, And the PN code uniquely identifies a transmitting entity of the wideband pilot. delete The method of claim 1, Scaling the sequence of pilot chips with a scaling factor to obtain a sequence of scaled pilot chips; Wherein the scaling factor is indicative of a transmit power level for the wideband pilot, and wherein the sequence of scaled pilot chips is time division multiplexed with the sequence of data chips. The method of claim 1, And the TDM sequence of pilot and data chips is transmitted on the reverse link of the wireless multi-carrier communication system. An apparatus of a wireless multi-carrier communication system, Means for processing one or more pilot symbols into a pseudo random number (PN) code to obtain a sequence of pilot chips for a wideband pilot; Means for processing the data symbols according to a multi-carrier modulation scheme to obtain a sequence of data chips; Means for time division multiplexing the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips; And Means for transmitting a TDM sequence of the pilot and data chips, The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Device of a wireless multi-carrier communication system. An apparatus of a wireless multi-carrier communication system, A modulator operative to process data symbols according to a multi-carrier modulation scheme to obtain a sequence of data chips; A pilot generator operative to process one or more pilot symbols into a pseudo random number (PN) code to obtain a sequence of pilot chips for a wideband pilot; A multiplexer operative to time division multiplex (TDM) the sequence of pilot chips with the sequence of data chips to obtain a TDM sequence of pilot and data chips; And A transmitter unit operative to process and transmit a TDM sequence of pilot and data chips, The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Device of a wireless multi-carrier communication system. A terminal comprising the apparatus of claim 9. A base station comprising the apparatus of claim 9. In a wireless multi-carrier communication system, one or more pilot symbols are processed into a pseudo random number (PN) code to obtain a sequence of pilot chips for a wideband pilot; Processing the data symbols according to a multi-carrier modulation scheme to obtain a sequence of data chips; Storing instructions operable to time division multiplex the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips, The TDM sequence of pilot and data chips is processed and transmitted over a communication channel of the wireless multi-carrier communication system, The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Processor Readable Media. A method of receiving a broadband pilot in a wireless multi-carrier communication system, Obtaining a sequence of received chips comprising a time division multiplexed (TDM) sequence of received pilot and data chips; Demultiplexing the received sequence of chips to obtain a sequence of received pilot chips and a sequence of received data chips for the wideband pilot; Processing the received sequence of pilot chips with a pseudo random number (PN) code to obtain a plurality of channel response estimates for a plurality of subbands; And Processing the received sequence of data chips according to a multi-carrier demodulation scheme and the plurality of channel response estimates to obtain recovered data symbols; The wireless multi-carrier communication system includes a plurality of subbands, wherein the recovered data symbols are obtained from different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. , Broadband pilot reception method. The method of claim 13, The wireless multi-carrier communication system is an orthogonal frequency division multiple access (OFDMA) communication system, and the multi-carrier demodulation scheme is for orthogonal frequency division multiplexing (OFDM). The method of claim 13, Processing the received sequence of pilot chips, Obtaining a plurality of channel gain estimates for a plurality of propagation paths for the wideband pilot; Processing the plurality of channel gain estimates to obtain a sequence of chip-spaced gain values; And Converting the sequence of chip-spaced gain values to obtain the plurality of channel response estimates for the plurality of subbands. The method of claim 15, The plurality of channel gain estimates are obtained with a rake receiver having a plurality of finger processors, each finger processor being operative to process a different one of the plurality of propagation paths to provide a channel gain estimate for the propagation path. , Broadband pilot reception method. delete An apparatus of a wireless multi-carrier communication system, Means for obtaining a sequence of received chips comprising a time division multiplexed (TDM) sequence of received pilot and data chips; Means for demultiplexing the received sequence of chips to obtain a sequence of received pilot chips and a sequence of received data chips for a wideband pilot; Means for processing the received sequence of pilot chips into a pseudo random number (PN) code to obtain a plurality of channel response estimates for a plurality of subbands; And Means for processing the received sequence of data chips according to a multi-carrier demodulation scheme and the plurality of channel response estimates to obtain recovered data symbols, The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Device of a wireless multi-carrier communication system. An apparatus of a wireless multi-carrier communication system, A demultiplexer operative to demultiplex a sequence of received chips including a time division multiplexed (TDM) sequence of received pilot and data chips to provide a sequence of received pilot chips and a sequence of received data chips for a wideband pilot ; A rake receiver operative to process the received sequence of pilot chips into a pseudo random number (PN) code to obtain a plurality of channel gain estimates for a plurality of propagation paths for the wideband pilot; A processor operative to process the plurality of channel gain estimates to obtain a plurality of channel response estimates for a plurality of subbands; And A demodulator operative to process the received sequence of data chips according to a multi-carrier demodulation scheme and the plurality of channel response estimates to obtain recovered data symbols, The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Device of a wireless multi-carrier communication system. A method of transmitting a wideband pilot in a wireless multi-carrier communication system, the method comprising: Processing one or more pilot symbols with a pseudo random number (PN) code to obtain a sequence of pilot chips for the wideband pilot; Processing the data symbols according to a multi-carrier modulation scheme to obtain a sequence of data chips; Summing the sequence of pilot chips and the sequence of data chips to obtain a combined sequence of pilot and data chips; And Transmitting the combined pilot and data chips sequence; The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Wide band pilot transmission method. The method of claim 20, And wherein said wireless multi-carrier communication system is an orthogonal frequency division multiple access (OFDMA) communication system and said multi-carrier modulation scheme is orthogonal frequency division multiplexing (OFDM). The method of claim 20, Wherein the wideband pilot is transmitted continuously for the duration of the sequence of data chips. The method of claim 20, Wherein the one or more pilot symbols are spread spectrum into the PN code in the time domain using direct sequence spread spectrum processing to obtain the sequence of pilot chips. The method of claim 20, And the PN code uniquely identifies a transmitting entity of the wideband pilot. delete The method of claim 20, Scaling the sequence of pilot chips with a scaling factor to obtain a sequence of scaled pilot chips; The scaling factor is indicative of a transmit power level for the wideband pilot, and wherein the sequence of scaled pilot chips is summed with the sequence of data chips. The method of claim 20, And the combined sequence of pilot and data chips is transmitted on a reverse link of the wireless multi-carrier communication system. An apparatus of a wireless multi-carrier communication system, Means for processing one or more pilot symbols into a pseudo random number (PN) code to obtain a sequence of pilot chips for a wideband pilot; Means for processing the data symbols according to a multi-carrier modulation scheme to obtain a sequence of data chips; Means for summing the sequence of pilot chips and the sequence of data chips to obtain a combined sequence of pilot and data chips; And Means for transmitting the combined pilot and data chips sequence; The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Device of a wireless multi-carrier communication system. A method of receiving a broadband pilot in a wireless multi-carrier communication system, Obtaining a sequence of received chips comprising a sequence of combined pilot and data chips transmitted by a transmitting entity, wherein the sequence of combined pilot and data chips is a sequence of pilot chips for the wideband pilot at the transmitting entity Obtaining the sequence of received chips, obtained by summing a sequence of data chips with; Processing the received sequence of chips into a pseudo random number (PN) code to obtain a plurality of channel response estimates for a plurality of subbands for the transmitting entity; And Processing the received sequence of chips according to a multi-carrier demodulation scheme and the plurality of channel response estimates to obtain recovered data symbols for the transmitting entity; The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Wide band pilot reception method. 30. The method of claim 29, Processing the received sequence of chips into a PN code, Obtaining a plurality of channel gain estimates for a plurality of propagation paths for the transmitting entity; Processing the plurality of channel gain estimates to obtain a sequence of chip-spaced gain values; And Converting the sequence of chip-spaced gain values to obtain the plurality of channel response estimates for the plurality of subbands for the transmitting entity. 31. The method of claim 30, The plurality of channel gain estimates are obtained with a rake receiver having a plurality of finger processors, each finger processor being operative to process a different one of the plurality of propagation paths to provide a channel gain estimate for the propagation path. , Broadband pilot reception method. 30. The method of claim 29, Estimating interference due to the wideband pilot; And Canceling the estimated interference from the received sequence of chips, thereby obtaining a sequence of received data chips, And the received sequence of data chips is processed to obtain the recovered data symbols. 30. The method of claim 29, The wireless multi-carrier communication system is an orthogonal frequency division multiple access (OFDMA) communication system, and the multi-carrier demodulation scheme is for orthogonal frequency division multiplexing (OFDM). An apparatus of a wireless multi-carrier communication system, Means for obtaining a sequence of received chips comprising a sequence of combined pilot and data chips transmitted by a transmitting entity, wherein the sequence of combined pilot and data chips comprises a sequence of pilot chips for a wideband pilot at the transmitting entity. Means for obtaining the sequence of received chips, obtained by summing a sequence of data chips; Means for processing the received sequence of chips into a pseudo random number (PN) code to obtain a plurality of channel response estimates for a plurality of subbands for the transmitting entity; And Means for processing the received sequence of chips according to a multi-carrier demodulation scheme and the plurality of channel response estimates to obtain recovered data symbols for the transmitting entity; The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Device of a wireless multi-carrier communication system. An apparatus of a wireless multi-carrier communication system, A rake receiver operable to process a sequence of received chips into a pseudo random number (PN) code to obtain a plurality of channel gain estimates for a plurality of propagation paths for a transmitting entity, the sequence of received chips being: The rake receiver transmitted by the transmitting entity and comprising a sequence of combined pilot and data chips obtained by summing a sequence of pilot chips and a sequence of data chips for a wideband pilot at the transmitting entity; A processor operative to process the plurality of channel gain estimates to obtain a plurality of channel response estimates for a plurality of subbands; And A demodulator operative to process the received sequence of chips according to a multi-carrier demodulation scheme and the plurality of channel response estimates to obtain recovered data symbols for the transmitting entity; The wireless multi-carrier communication system includes a plurality of subbands, wherein the data symbols are transmitted on different ones of the plurality of subbands at different time intervals determined by a frequency hopping (FH) sequence. Device of a wireless multi-carrier communication system.

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